A. c. attachment plug with automatic circuit breaker



M. A. AUTH Dec. 27. 1955 A.C ATTACHMENT PLUG WITH AUTOMATIC CIRCUITBREAKER Filed Aug. 17, 1954 lNVENTOR %MQ J ATTORNEYS v/gilv 0/0 :5335

nited States Patent A. C. ATTACHMENT PLUG WITH AUTOMATIC CHKCUIT BREAKERMaximilian A. Auth, Stratford, Conn., assignor of onethird to M. A.Auth, Incorporated, Stratiord, Conn, a corporation of Connecticut;one-=third to Marietta Haythorue, New York, N. Y., and one-third toHarold K. Andrews, Stratford, Conn.

breaker, and has for an object to provide an attachment plug forplugging into electrical outlet receptacles to supply electric currentto various devices, as household electrical devices or attachments, inwhich the circuit isautomatically made and broken in the plug by the:act of either inserting the plug into or removing it .from thereceptacle.

Another object is to provide a device of this character which may beused both as an attachment plug for use in supplying current to thevarious electrical devices, and as a connector for use with a standardattachment plug.

Another object is to provide a device ofthis character which is of verysimple construction and may be manufactured at low cost.

With the foregoing and other objects in view, I have devised theconstruction illustrated in the accompanying drawing forming a part ofthis specification. It is, how ever, to be understood the invention isnot limited to the specific details of construction and arrangementshown, but may embody various changes and modifications within the scopeof the invention.

In this drawing:

Fig. l is a side elevation of the internal elements of an attachmentplug involving this invention, showing them mounted in one of theinsulating body members, and with one half of the insulating bodyremoved;

Fig. 2 is a side view of the assembled plug looking from the right ofFig. l, but with both body members assembled;

Fig. 3 is a view similar to Fig. l, but showing in section a wall outletreceptacle into which this plug is inserted;

Figs. 4 and 5 are transverse sections substantially on lines 44 and 5-5respectively of Fig. 1;

Fig. 6 is a perspective view of one of the blade contacts;

Fig, 7 is an inside view of one of the body members with the variouselectrical contacts removed;

Fig. 8 is a perspective view of one of the stationary contacts, and

Fig. 9 is a view similar to Fig. 1, showing the plug modified so that itmay be used as a connector for use with standard attachment plugs.

In withdrawing the usual attachment plug from a wall outlet receptacle,there is likely to be arcing between the plug contacts and thereceptacle contacts, as the plug contacts separate from the receptaclecontacts, and this may cause fire, explosion or a short circuit undercertain conditions. it is, therefore, an object of this invention toprovide an attachment plug which is so constructed as to break thecircuit in the plug itself and outside the receptacle when withdrawingthe plug from the receptacle, the circuit being broken in the plugbefore the plug contacts are separated from the receptacle contacts, sothat there will be no breaking of the live circuit and therefore noarcing in the outlet receptacle itself, but

spaced somewhat from each other.

2,728,823 Patented Dec. 27, 1955 any arcing would occur within the plugitself and outside the receptacle instead of in the receptacle.

The device of Figs. 1 to 7 comprises an insulating body member 10comprising two sections 11 of insulating ma terial placed side by side,and when assembled connected by any suitable means, such as the crossbolt 12. These two body members preferably are molded of insulatingmaterial and are identical so that they may be formed from the same die.Mounted in this body are two or more blade contacts 13, in the presentcase the usual two, for insertion in any standard type of wall outletreceptacle 14, or suitable connector, having stationary receptaclecontacts 15 connected to the usual house Wiring system (not shown),the-blades 13 being insertabie through the usual slots 16 in the frontplate 17 of the receptacle to engage the receptacle contacts 15. Theblade contacts 13 in the form shown each comprise a flat strip ofresilient conductor metal bent upon itself intermediate its length at 18forming the free end of the blade, and inner and outer side members 19and 20 side by side but normally The inner member 19 is substantiallystraight and anchored or secured at its 'free end in the body 141'- Asimple and effective means for securing this member and therefore theblade inthe body is to provide it with a substantially L-shapedoifsetincluding a free end portion 21 connected by the intermediate portion 22at substantially right angles to the straight portion of the member 19,and this offset seating in a similar L-shaped recess 23 formed a half inthe inner face of each of the body members 11, so that when assembledthe contact blade is mounted partly in each ofthe body members 11. Whenso mounted, the outer member 20 of each blade extends through a slot oropening 24 in the end wall 25 of the body into a chamber 26 formed bylongitudinal channels in the inner walls of the body members 11, whichchannels in the two body members arein alignment and face each other toform the chamber 26. The free end portion 27 of the outer member 20 ismovable laterally in this chamber and forms one element of a switch, theresilient action of the metal forming this member tending to hold it inits outer position against the outer wall of the chamber 26, as shown inFig. l. The exposed portion of the member 20 is also inclined, as shownin Fig. 1, from its free end 18 inwardly, and outwardly away from thesection 1 19 toward the body 10.

29 in the inner surface of each of the body members 11,

with this plate opposite to the free end 27 or" the blade contact. Attheir outer ends the plates 28 are located in chambers 29a in the body,and each has on its opposite edges laterally bent flanges 30 betweenwhich is mounted any suitable means for securing the conductor wires 31in an insulated cord 32 to the stationary contacts 23. In this case thesecuring means comprises the usual binding post screw 33 threaded intothe contact plate 28. The cord 32 and the conductor wires pass through asuitable inlet passage 34 leading inwardly from the end Wall of the bodyto the chambers 29a and formed by channels half in each of the innersurfaces of the members 11.

Referring to Fig. 1, it will be seen the free end portions 27 of thecontact blades are movable to and from the stationary contacts 28, andto increase the life of these contacts and prevent burning out byarcing, each of the contacts 27 and 28 may be provided with silver orsimilar contacts 35 and 36 respectively, which engage each other whenthe movable contact 27 engages the stationary contact 28.

The use and operation of the device is illustrated in 3 Fig. 3. of theblade contacts 13 are normally separated from the stationary contacts 28by the resilient action of the blades 13. When these blades 13 areinserted into the slots 16 in the face of the receptacle 14, as theouter portions 24) of the blades are inclined they have a camming actionon the sides of these slots and the stationary contacts within thereceptacle, forcing the free end portions 27 inwardly toward thestationary contacts 28, and as they engage these contacts 28 they closethe circuit from the receptacle contacts 15 to the conductor wires inthe cord 32 leading to the electrical attachment to be operated. Theblade contacts 13 are so designed and arranged that the contacts 35 and36 do not come together until after the exposed portions of the blades13 are in engagement with the receptacle contacts 15. For this reason,when withdrawing the plug from the receptacle, the blades 13 are stillin engagement with the receptacle contacts 15 when the free ends 27carrying the contacts 35 separate from the stationary contacts 36, thusbreaking the live circuit in this plug instead of in the receptacle.Thus when the blade contacts 13 separate from the receptacle contacts 15they are already in a dead or open circuit and there is no arcingbetween the contacts 13 and the receptacle contacts 15. Any arcing istherefore within the plug and outside the receptacle instead of in thereceptacle. Arcing is also reduced because both sides of the circuit arebroken at the same time.

In the form of Figs. 1 to 7, the means shown for connecting theconductor wires of the insulating cord 32 from the attachment to beoperated with the stationary contacts 28 and 36 are indicated as bindingpost screws 33. In Fig. 9, a somewhat different means for electricallyconnecting these conductors with the stationary contacts 36 is shown asresilient spring receptacle contacts 37, these comprising substantiallyU-shaped spring contacts bent upon themselves at 38 forming a springblade 39 inclined inwardly from inlet slots 40 in the end of theinsulating body 41 corresponding to the body 10, these slots 40 leadingto the chambers 42 in which the contacts 37 are mounted. The other endof the spring contact 37 comprises a flat plate 43 of the same size andshape as the blade 28 and mounted in the body members 41 in slots 29,the same as in the first form, and each plate 43 carries the stationarycontact 36 opposite the movable contact 35 of the plug contact blades13. The stationary contacts 43 and the blade contacts 13 are the same asin the form of Figs. 1 to 7, and cooperate in the same way to make andbreak the circuit when plugged into a wall outlet receptacle, asindicated in Fig. 3, the only change being that instead of the bindingpost screws 33, as shown in the first form, for connecting the cordconductors 31 to the stationary contacts, receptacle or connectorcontacts 39 are mounted in suitable chambers in the body and the end ofthe body is provided with inlet slots 40 leading to the connectorcontacts 39, so that the contact blades of the standard attachment plugcan be inserted in these slots 49 to engage the connector contacts 39for supplying current to the attachment to be operated. Thus thecontacts 39 function as means for connecting the conductor wires 31 fromthe attachment to be operated with the stationary contacts 36 in thisform the same as do the binding post screws 33 in the first form. Thisstructure of Fig. 9, therefore, makes it unnecessary to disassemble thisplug to connect these conductor wires with the attachment plug, as isrequired in the form of Figs. 1 to 7, it being necessary, to secure theadvantages of this improved plug, merely to plug the standard attachmentplug blades into the slots 40.

To facilitate use of the device in plugging it into and removing it fromthe wall outlet receptacle, the body 10 or 41 may be provided withelements to improve the hand grip on this member in inserting it orremoving it from the receptacle. For this purpose, at the outer end ofthe body and on its opposite side edges it is provided As previouslyindicated, the free end portions 27 with rounded nubs or bosses 44.These will increase the hand grip on the body. They could be located onthe opposite fiat sides of the body, but it is preferred to place themon the narrower side edges, as in this case they do not increase theeffective thickness of the body, which might be objectionable if theplug is used in duplex or similar multiple receptacles, so that theplugs lie side by side. In other words, placing these grips on thenarrower surfaces of the body provides greater clearance between theplugs when two or more are plugged into a duplex or other multiplereceptacle.

It will be seen from the above that this is a very simple deviceinvolving a minimum number of parts, and that in use the circuit to theattachment to be operated is made and broken in the plug itself insteadof in the wall outlet receptacle, and that any arcing caused by thismaking and breaking of the circuit therefore occurs within the plug andoutside of the wall outlet receptacle, greatly reducing the danger ofexplosions, fires, or the like under certain conditions which mightoccur. Also it will be seen that this making and breaking of the circuitwithin the plug is performed automatically by the mere act of insertingthe blades of the plug in the wall outlet receptacle and removing themtherefrom with the same operations as is used with the standardattachment plug not provided with this safety feature.

Having thus set forth the nature of my invention, I claim:

1. In an electrical device of the character described, a body member ofinsulating material, attachment plug contacts projecting from one end ofthe body and adapted for insertion in the entrance slots of an electricreceptacle to engage the contacts therein, each of said plug contactscomprising a strip of resilient metal folded upon itself forminglaterally spaced members side by side with the folded end forming thefree outer end of the contact, the free end of one of said side memberssecured in the body, stationary contact members in the body, the freeends of the other side members of the plug contacts being movable to andfrom engagement with the stationary con tacts and normally held spacedtherefrom by the resilient action of said strips, the free side membersof the plug contacts being inclined so that as they are inserted in thereceptacle they will have a camming action therewith to shift saidmovable free ends of the plug contacts into engagement with thestationary contacts to close a circuit therewith, and means forconnecting conductor wires with the stationary contacts.

2. In an electrical device of the character described, a body member ofinsulating material, attachment plug contacts projecting from one end ofthe body and adapted for insertion in the entrance slots of an electricreceptacle to engage the contacts therein, each of said plug contactscomprising laterally spaced side members connected at their outer ends,the other end of one of the side members being secured in the body,stationary contacts in the body, the free end of the other side memberbeing movable to and from a stationary contact and normally separatedtherefrom by resilient action of said member, said latter side membersbeing inclined so that as they are inserted in the receptacle they havea camming action therewith to shift their free ends into engagement withthe stationary contacts, and means for connecting conductor wires withthe stationary contacts.

v3. In an electrical device of the character described, a body member ofinsulating material, attachment plug contacts projecting from one end ofthe body and adapted for insertion in the entrance slots of an electricreceptacle to engage the contacts therein, each of said plug contactscomprising laterally spaced side members connected at their outer ends,the other end of one of the side members being secured in the body,stationary contacts in the body opposite the inner free ends of theother side members of the plug contacts, the latter side members of theplug contacts being inclined outwardly and inwardly toward their outerends and resilient so that their inner free ends are normally heldspaced from the stationary contacts by their resilient action, saidinclined members adapted to have a camming action with the receptaclewhen inserted therein to shift their inner free ends into engagementwith the stationary contacts, and means in the body for connectingconductor wires with the sta tionary contacts.

4. In an electrical device of the character described, a body member ofinsulating material, attachment plug contacts projecting from one end ofthe body and adapted for insertion in the entrance slots of an electricreceptacle to engage the contacts therein, the plug contacts eachcomprising a pair of side members arranged side by side connected attheir outer ends and one of each pair secured at its inner end in thebody, the others of said side members having free ends within the body,stationary contacts in the body opposite the free ends of the latterside members, said latter side members being resilient and normallyspaced at their inner free ends from the stationary contacts by theirresilient action, said latter side members being longitudinally inclinedso that they will have a camming action with the receptacle wheninserted therein to shift their inner free ends into engagement with thestationary contacts, and means in the body for connecting conductorwires with the stationary contacts.

5. In an electrical device of the character described, a body member ofinsulating material, attachment plug contacts projecting from one end ofthe body and adapted for insertion in the entrance slots of an electricreceptacle to engage the contacts therein, the plug contacts includingside members having free ends within the body, stationary contacts inthe body opposite the free ends of the side members, said side membersbeing resilient and normally spaced at their inner free ends from thestationary contacts by their resilient action, said side members beinglongitudinally inclined so that they will have a camming action with thereceptacle when inserted therein to shift their inner free ends intoengagement with the stationary contacts, means in the body forconnecting conductor wires with the stationary contacts comprisingconnector contacts mounted in the body and connected with the stationarycontacts, and said body provided with entrance slots leading to theconnector contacts for insertion of the contact blades of standardattachment plugs to engage the connector contacts.

6. In an electrical device of the character described, a body ofinsulating material comprising a pair of like members side by side, theopposed inner faces of said members being formed with opposed alignedgrooves and opposed channels opening through one end of the body formingchambers therein, attachment plug contacts projecting from the end ofthe body each including laterally spaced side members connected at theirouter ends, the inner end of each of one of said side members beingseated in said grooves to mount the contacts in the body with the innerends of the other side members located in the said chambers, said bodymembers also provided with other aligned grooves in their inner faces,stationary contacts comprising plates seated at their opposite edges insaid latter grooves and located opposite the free ends of the secondside members of the plug contacts, said second side members beingresilient so as to hold their inner free ends spaced from the stationarycontacts by their resilient action and longitudinally inclined so thatthey will have a camming action with the receptacle when insertedtherein to shift their inner free ends into engagement with thestationary contacts, and means in the body for connecting conductorwires with the stationary contacts.

References Cited in the file of this patent UNITED STATES PATENTS2,005,441 Shearer June 18, 1935 2,013,596 Becker Sept. 3, 1935 2,245,986Krauss June 17, 1941 2,419,585 OBrien et a1 Apr. 29, 1947 2,452,967Thomas Nov. 2, 1948

